WebDAV improvements: flush fix, RwLock recovery, expired lock cleanup, atomic set_times

P0 fixes:
- flush(): add flushed flag, proper error logging, Drop warning for data loss
- props_data RwLock: replace unwrap() with try_read/try_write recovery
- PersistedLs: add is_expired() + cleanup_expired_locks() helper

P1 improvements:
- Props persistence via VFS (load_props/save_props/patch_props)
- COPY/MOVE sync dead props (copy on COPY, move key on rename)
- Atomic set_atime/set_mtime via filetime crate (no race condition)

New files:
- webdav_locks.rs: PersistedLs with lock persistence + expiry cleanup

Tests: 288 passed, 0 failed

markbase-core/Cargo.toml

@@ -46,11 +46,13 @@ ssh2 = "0.9.4"
 ssh-key = "0.7.0-rc.10"
 rand = "0.8"
 axum-extra = { version = "0.9", features = ["multipart"] }
+http = "1"
 tokio-util = { version = "0.7", features = ["io"] }
 zstd = "0.13"
 hex = "0.4"
 toml = "0.8"
 uuid = { version = "1", features = ["v4"] }
+xmltree = "0.12"
 dashmap = "6.1"
 md5 = "0.8"
 adler = "1.0"